Palmitic Acid and off-brand discs

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emorritt
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Location: Tennessee

Palmitic Acid and off-brand discs

Post: # 48553Unread post emorritt
Fri Nov 24, 2017 4:20 pm

OK, I've been going through my collection which includes a lot of older blanks and I've noticed that only certain older recording discs - never recorded on - are leaching palmitic acid, others are not. Primarily, Allied, Audiodisc and some Reeves Soundcraft are turning white, while Federal, Duodisc, Wilcox-Gay, Tempo-Tone, RecordDisc, Presto and a few other dime store brands are not. Anybody have an explaination for this? Maybe Ron Leeper? It seems strange that some of the major brands are deteriorating and other lesser brands are not; but Presto discs - a major brand, which I think their coating formulation was based on the Pyral lacquer - are not breaking down. I've had most of these blanks for at least 25 - 30 years and when I originally picked them up, all were clean, clear, smooth, etc. (Obviously not fit for cutting because of their age, but interesting artifacts nonetheless.) Anybody have any insight on this?

Thanks!

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SueDenim
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Re: Palmitic Acid and off-brand discs

Post: # 48556Unread post SueDenim
Sat Nov 25, 2017 6:42 am

If it looks like grey oily/waxy stuff on the surface, then it's the plasticizer coming out.
This was used in the original formulation of the lacquer to, basically, enable easier/quieter cuts.

It can be cleaned (see below), but I wouldn't try to cut such a blank after you've done this as it'll sound rotten and probably take hours off your cutting stylus!
https://www.nedcc.org/audio-preservation/cleaning-discs

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emorritt
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Joined: Thu Nov 09, 2006 2:03 pm
Location: Tennessee

Re: Palmitic Acid and off-brand discs

Post: # 48559Unread post emorritt
Sat Nov 25, 2017 1:09 pm

Thanks Sue! Yes, I've cleaned discs for transfer/preservation for many years. I'm just interested in what's different between the formulations used for "dime store" blanks (like DuoTone, Wilcox-Gay, Recordisc, etc.) that don't seem to be breaking down and the "pro" products like Audiodisc, Soundcraft, etc. I have quite a number of Presto blanks in all sizes, green seal, black seal, etc. but none of them exhibit the breakdown as well as the dime-store products. I know that the larger manufacturers that served the industry also served the home recording consumers as well and many had a separate production line for "home" blanks, probably with a different formulation of lacquer. Maybe not as much plasticizer since it's not separating from the disc coating??

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